绿色木霉粗纤维素酶液水解壳聚糖的研究

利用自制绿色木霉粗纤维素酶液降解壳聚糖制备低聚壳聚糖.采用粘度法、乙酰丙酮法和还原糖浓度分析,研究了温度、pH值及反应时间等因素对壳聚糖水解程度和产物相对分子质量的影响,并采用质谱法对水解产物进行定性分析.结果表明,粗纤维素酶液水解壳聚糖作用的最适pH为5.0、最适反应温度为50 ℃、最适反应时间为12 h.粗纤维素酶...     

桦褶孔菌漆酶固定化及其对染料的降解

采用壳聚糖交联法和海藻酸钠-壳聚糖包埋交联法固定化桦褶孔菌产生的漆酶,探讨最佳固定化条件,固定化漆酶的温度,pH稳定性及操作稳定性,并以两种固定化酶分别对4种染料进行了降解.结果表明:(1)壳聚糖交联法固定化漆酶的最佳条件为:壳聚糖2.5%,戊二醛7%,交联时间2h,固定化时间5h,给酶量1g壳聚糖小球:1mL酶液(1U/mL),固定化效率56%;(2)海藻酸钠-壳聚糖包埋交联法固定化漆酶的最佳条件为:海藻酸钠浓度4%,壳聚糖浓度0.7%,氯化钙浓度5%,戊二醛浓度0.6%,给酶量4mL 4%海藻酸钠:1mL酶液(1U/mL),固定化效率高达86%;(3)固定化的漆酶相比游离漆酶有更好的温度和pH稳定性;(4)比较两种固定化漆酶,海藻酸钠-壳聚糖包埋交联法固定化酶的温度及酸度稳定性要优于壳聚糖固定化酶,但可重复操作性要弱于后者,两者重复使用8次后的剩余酶活比率分别为71%及64%;(5)两种固定化酶对所选的4种不同结构的合成染料均有较好的降解效果,其中壳聚糖固定化酶对茜素红的降解效果及重复使用性极佳,重复降解40mg/L的茜素红10次,降解率仍保持在100%.     

多种农药与次氯酸钠、高锰酸钾和高铁酸钾的反应活性

为探究4类,10种广泛使用的农药(苯氧羧酸类,芳香酸类,取代脲类和烟碱类)与3种氧化剂(次氯酸钠,高锰酸钾和高铁酸钾)的反应活性,本研究在温度(25±2)℃、pH值为8的条件下,分析10种农药分别与3种氧化剂NaClO、KMnO4、K2Fe O4在不同浓度下的反应活性,采用HPLC检测法,对比降解效能,探究氧化剂性质与有机物结构导致的反应活性的差异。实验结果表明,不同种类农药的结构性质对反应活性有重要影响,3种氧化剂的氧化降解能力有明显差异。苯氧羧酸类和芳香酸类农药结构较简单,并含有稳定的苯环或吡啶环结构,氧化降解较困难。取代脲类和烟碱类农药结构较复杂,氧化剂可攻击其不饱和官能团,反应活性较高。NaClO对取代脲类农药的降解率明显优于其他2种氧化剂,3种氧化剂对烟碱类农药的氧化降解效果依次为NaClO>KMn O4>K2Fe O4。研究多种农药与次氯酸钠、高锰酸钾和高铁酸钾的反应活性对降解去除水体中的农药残留对水环境的治理具有重要意义。     

壳聚糖辐照降解产物涂膜保鲜草莓研究

壳聚糖具有抑菌性与成膜性。将壳聚糖辐照降解得到的一系列不同粘均分子量产物进行涂膜草莓保鲜,研究涂膜液中壳聚糖粘均分子量、浓度、pH值、有机酸、明胶含量对草莓保鲜效果的影响;并设计四因素三水平正交试验。实验结果表明：1％（w／v）7．0×10^4Da壳聚糖、1％（v／v）醋酸、pH5、添加明胶0．5％的涂膜配方具有最好的保鲜效果;在常温（20℃、湿度80％～90％）下可以延长贮藏期2d;低温（3℃-4℃、湿度80％-90％）下可以延长贮藏期3d。     

羧甲基壳聚糖的制备及其在保鲜中的应用

研究了在碱性条件,无溶剂体系下壳聚糖羧甲基化制备工艺,通过IR对反应前后壳聚糖结构进行了表征。最佳反应条件：2g壳聚糖,在NaOH加入量为5g、碱化时间为6h、氯乙酸用量为6g、3％KI、反应时间为8h、反应温度60℃,产品取代度为1．27。同时研究了羧甲基壳聚糖对辣椒、猪肉涂膜保鲜实验,结果显示对辣椒、猪肉具有较好的涂膜保鲜作用。     

脱乙酰壳聚糖固定化宇佐美曲霉木聚糖酶及固定化酶的性质和应用(英文)

研究壳聚糖吸附和戊二醛交联对木聚糖酶固定化条件 .将酶液加入到经醋酸溶液处理过的脱乙酰壳聚糖的pH 4 8的悬液中 ,加入浓度为 0 3%～ 0 4 %的戊二醛溶液 ,室温下 ,8h后得到固定化酶 .固定化酶的半失活温度比游离酶高 ,由 5 1℃升至 71℃ ,Km 值由游离酶的 1 2mg ml增加到1 5mg ml ,最适反应温度也由 5 5℃增加到 71℃ ,而最适反应pH由 4 6下降到 3 8.该固定化木聚糖酶可用于制造低聚木糖 .经过 10次连续应用实验后 ,该固定化酶的活力保持 81%     

不同价态铁元素对厌氧微生物降解2,4,6-三氯酚的影响

【目的】考察初始pH值为5.0?10.0时, 不同价态铁元素(Fe0、Fe2+和Fe3+)对厌氧微生物降解2,4,6-三氯酚(2,4,6-TCP)的影响。【方法】采用间歇试验, 接种驯化3个月的厌氧污泥, 向其中分别投加Fe0、Fe2+和Fe3+, 测定体系中2,4,6-TCP浓度、pH值、铁离子浓度和微生物脱氢酶活性。【结果】“Fe0/Fe2+/Fe3+-微生物”体系对2,4,6-TCP的降解效率, 在初始pH值为中性偏酸性时, “Fe2+-微生物”体系>“Fe0-微生物”体系>“Fe3+-微生物”体系; 而当初始pH值为碱性时, “Fe0-微生物”体系>“Fe2+-微生物”体系>“Fe3+-微生物”体系; “Fe0/Fe2+/Fe3+-微生物”三种体系均有调节pH值的能力, 其中“Fe0-微生物”体系调节能力最强; 在不同初始pH值条件下不同价态铁元素对厌氧微生物活性的影响结果与其对2,4,6-TCP的影响规律基本相同。【结论】不同价态铁元素对厌氧微生物降解2,4,6-TCP的影响与初始pH值、体系实时pH值和铁元素价态及浓度等因素有关。     

菜子油酸的环氧化研究

以732型强酸性阳离子交换树脂作催化剂,对菜子油酸的环氧化反应作了研究,考察了反应温度、H_2O_2浓度、催化剂用量、不同有机酸及DBP有机介质对环氧化的影响.研究结果表明:较适宜的反应温度为50℃,催化剂用量为菜子油酸重量的10%～15%,所使用H_2O_2的浓度应高于30%.在DBP的保护下,产物最高环氧值可达3.3%.     

玻璃负载TiO2膜光催化降解垃圾渗滤液的研究

研究了以SOL=GEL法制备的TiO₂膜光催化降解垃圾渗滤液的可行性,探讨了负载TiO₂膜的影响因素及TiO₂膜的催化活性,TiO₂膜的最佳煅烧温度为450℃.测定了反应时间、进水浓度、pH值、光源强度等因素对垃圾渗滤液的COD_Cr和色度去除率的影响.光强越大,催化效果越好,光照时间越长,催化效果越好;溶液的初始浓度越大,降解率越低;反应液的在偏酸、碱的条件下有利于光催化氧化反应的进行.在最佳的实验条件下,TiO₂膜的煅烧温度为450℃,溶液的pH值为3~4,垃圾渗滤液的初始COD_Cr为537mg·L^-1,光催化降解2h,COD_Cr和UV335的去除率分别为94.4%和96.9%.     

Fe掺杂纳米ZnO光催化处理硝基苯废水

以高压荧光汞灯为光源,以自制Zn1-xFexO为催化剂,研究了悬浆体系中硝基苯污染废水的降解过程及降解规律。考察了硝基苯初始质量浓度、Zn1-xFexO光催化剂的质量浓度、Fe与Zn摩尔比值以及反应温度、pH、反应时间对硝基苯降解过程的影响。结果表明:以Zn1-xFexO作为催化剂可以有效地去除废水中的硝基苯,同时硝基苯的光催化降解过程符合一级反应动力学模型;反应活化能为9.3 k J·mol-1;当Zn0.99Fe0.01O的质量浓度为0.8 g·L~(-1)(Fe/Zn摩尔比为1∶99)、在125 W高压荧光汞灯照射下、硝基苯的初始浓度为400 mg·L~(-1)、反应温度为30℃、pH为3.27、取样时间为4 h时,硝基苯废水的反应速率常数和去除率分别为0.0136 min-1和98.88%;硝基苯的去除率和反应速率常数与Zn0.99Fe0.01O的质量浓度、Fe/Zn掺杂比例以及硝基苯初始浓度、溶液pH、反应温度等因素有关;同时,自制的Zn0.99Fe0.01O催化剂显著降低了反应活化能,从而提高了硝基苯污染废水的光降解效果。     

BCL2-CISD2

CISD2, an ER BCL2-associated autophagy regulator also known as NAF-1, is responsible for the human degenerative disorder Wolfram Syndrome 2. In order to interrogate the physiological role of CISD2 we generated and characterized the Cisd2 gene deletion in mice. Cisd2 null mice manifest significant degeneration in skeletal muscle tissues, which is accompanied with augmented autophagy, dysregulated Ca²⁺ homeostasis and elongated mitochondria. Our findings describe a novel role for BCL2-CISD2 in the homeostatic maintenance of skeletal muscle. It remains to be elucidated how and if the antagonism of the BECN1 autophagy-initiating complex and modulation of ER Ca²⁺ homeostasis by BCL2-CISD2 are interconnected.     

Synthesis of [11-2H2], [8-2H2], [7-2H2], [6-2H2], [5-2H2], [4-2H2] and [3-2H2] cis-9-octadecenoates

Deuterated oleates have been synthesized by semihydrogenation of acetylenic intermediates. [11-²H₂]Oleate was prepared by two-carbon chain extension of the C₁₆ alcohol obtained from [1-²H₂]octyl bromide and 7-octyn-1-ol. [8-²H₂] and [7-²H₂]oleates were both prepared from dimethyl suberate, tetradeutero intermediate C₁₆ alcohols were synthesized from [1,8-²H₄] and [2,7-²H₄]octane diols by monobromination, conversion to deuterated 9-decyn-1-ols and reaction with octyl bromide. Oxidation gave [8-²H₂]-9-octadecynoate and [2,7-²H₂]-9-octadecynoate, after semihydrogenation of the latter, deuterons at C-2 were removed by exchange with aqueous alkali. [6-²H₂] and [5-²H₂]oleates were obtained from methyl 5-tetradecynoate, semihydrogenation, deuterium exchange at C-2 and two malonate extensions gave [6-²H₂]oleate; reduction with lithium aluminum deuteride, two malonate extensions and semihydrogenation gave the [5-²H₂] ester. [4-²H₂] and [3-²H₂]oleates were both obtained from methyl 7-cis-hexadecenoate, exchange of the α protons and chain extension gave the [4-²H₂] ester and reduction with lithium aluminum deuteride and chain extension gave the [3-²H₂] ester.     

Synthesis and physicochemical properties of 2'-deoxy-2',2'-difluoro-beta-D-ribofuranosyl and 2'-deoxy-2',2'-difluoro-alpha-D-ribofuranosyl oligonucleotides

We present procedures for nucleoside and oligonucleotide synthesis, binding affinity (Tm) and structural analysis (CD spectra) of 2'-deoxy-2',2'-difluoro-alpha-D-ribofuranosyl and 2'-deoxy-2',2'-difluoro-beta-D-ribofuranosyl oligothymidylates. Possible reasons for the thermal instability of duplexes formed between these compounds and RNA or DNA targets are discussed.     

Stereospecific 2'-amination and 2'-chlorination of adenosine by Actinomadura in the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin

2'-Amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin (2'-CldCF) are two nucleoside antibiotics produced by Actinomadura. The biosynthesis of these two nucleoside antibiotics has been studied by the addition of [U-14C]adenosine with or without unlabeled adenine to cultures of Actinomadura. By this experimental approach, it is possible to demonstrate that adenosine is the direct precursor for the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-CldCF. These conclusions are based on the observation that the percentage distribution of 14C in the aglyconic and pentofuranosyl moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were similar to the distribution of 14C in the adenine and ribosyl moieties of the [U-14C]adenosine (i.e., 48:52) added to cultures of Actinomadura. Experimentally, the percentage distribution of 14C in the (i) adenine:2-amino-2-deoxy-beta-D-ribofuranose of 2'-amino-2'-deoxyadenosine is 51:49; (ii) 8-(R)-3,6,7,8-tetrahydroimidazo[4,5-d]-[1,3-diazepin-8-o1]:2 -chloro-2- beta-D-ribofuranose of 2'-CldCF is 45:55; and (iii) adenine:ribose of the adenosine isolated from the RNA of Actinomadura is 42:58. Further proof that adenosine is the direct precursor for the biosynthesis 2'-amino-2'-deoxyadenosine and 2'-CldCF was demonstrated by the addition of 75 mumol of unlabeled adenine together with [U-14C]adenosine to nucleoside-producing cultures of Actinomadura. The percentage distribution of 14C in the aglycon and the sugar moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were 46:54 and 47:53, respectively; the percentage distribution of 14C in the adenine and ribose moieties of the adenosine isolated from the RNA of Actinomadura was 51:49. These data show that the hydroxyl on C-2' of the ribosyl moiety of adenosine undergoes a replacement by a 2'-amino or a 2'-chloro group to form 2'-amino-2'-deoxyadenosine or 2'-CldCF with retention of stereconfiguration at C-2'. Finally, Actinomadura can utilize inorganic chloride from the medium as demonstrated by the isolation of [36Cl]2'-CldCF following the addition of [36Cl]chloride to the culture medium. Mechanisms for the regioselective modification of the C-2' hydroxyl group and stereospecific insertion of the amino and chloro groups are discussed.     

Stereospecific formation of alpha-hydroxycarboxylato oxo peroxo complexes of vanadium(V). Crystal structure of (NBu4)2[V2O2(O2)2(L-lact)2] x 2H2O and (NBu4)2[V2O2(O2)2(D-lact)(L-lact)] x 2H2O

An overview of structurally characterized alpha-hydroxycarboxylatodioxo- and alpha-hydroxycarboxylatooxoperoxovanadates(V) is presented and the geometric parameters of the V2O2 bridging core are discussed. The first case of a stereospecific formation of oxoperoxovanadates(V) is reported: The crystal structures of the isomeric compounds (NBu4)2[V2O2(O2)2(L-lact)2] x 2H2O and (NBu4)2[V2O2(O2)2(D-lact)(L-lact)] x 2H2O (lact = C3H4O3(2-), the anion of the lactic acid) differ mainly in the arrangement of the V2O2 core and in mutual orientation of the V=O bonds. The complexes with achiral ligands adopt the same structural type as the complexes formed from a racemic mixture of a chiral ligand, while the structure obtained using an enantiopure L,L-hydroxycarboxylate is different.     

Convenient synthesis of 2'-deoxy-2-fluoroadenosine from 2-fluoroadenine

A convenient synthesis of 2'-deoxy-2-fluoroadenosine from commercially available 2-fluoroadenine is described. The coupling reaction of silylated 2-fluoroadenine with phenyl 3,5-bis[O-(t-butyldimethylsilyl)]-2-deoxy-1-thio-D-erythro-pentofuranoside gave the corresponding 2-fluoro-2'-deoxyadenosine derivative (alpha/beta = 1:1) in good yield. The alpha- and beta-anomers were separated by chromatography, and then desilylated to give compounds 1a and 1b.     

Stereoselective Synthesis of 2-Amino-2-deoxy-d-arabinose and 2-Deoxy-d-ribose

An efficient method for the stereoselective synthesis of 2-amino-2-deoxy-d-arabinose and 2-deoxy-d-ribose is described.

The key step in this method was accomplished by the nucleophilic addition of methyl isocyanoacetate to 2,3-O-isopropylidene-d-glyceraldehyde with high erythro-selectivity (nearly 100%).

Subsequent intermolecular cyclization predominantly gave the desired oxazoline derivative (trans-form), in which two new chiral centers were formed. The oxazoline derivative was efficiently converted to both 2-amino-2-deoxy-d-arabinose and 2-deoxy-d-ribose.